NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part2/13755

Internet Message Format | 1996-08-05 | 2.2 KB

Path: nyssa.swt.edu!LN16674
From: [e-mail] (Leland Newsom)
Newsgroups: comp.lang.c
Subject: Re: reversing a string
Date: 10 Apr 1996 01:07:52 GMT
Organization: Southwest Texas State University
Message-ID: <4kf1l8$[e-mail]>
References: <4k6cjl$[e-mail]> <4kb1s7$[e-mail]> <[e-mail]>,<[e-mail]>
Reply-To: [e-mail]
NNTP-Posting-Host: nyssa.swt.edu

In article <[e-mail]>, [e-mail] (TRAN PHAN ANH) writes:
>Something like this?  Or is the s2 argument considered an extra variable.
>
>Anh

Yes, s2 would be considered an extra variable.
Leland


>
>
>#include <stdio.h>
>#include <string.h>
>
>void reverse(char *s1, char *s2)
>{
>  if(s1>=s2)
>    return;
>
>  *s1^=*s2;
>  *s2^=*s1;
>  *s1^=*s2;
>
>  reverse(s1+1,s2-1);
>}
>
>
>int main(int argc, char *argv[])
>{
>  printf("Arg: %s\n",argv[1]);
>
>  reverse(argv[1],&argv[1][strlen(argv[1])-1]);
>
>  printf("Result: %s\n",argv[1]);
>}
>
>
>
>
>
>In article <[e-mail]>, Lawrence Kirby <[e-mail]> writes:
>> In article <4kb1s7$[e-mail]>
>>            [e-mail] "John Murphy" writes:
>>
>>>In article <4k6cjl$[e-mail]>, [e-mail]
>>>says...
>>>>
>>>>I have a challenge from a friend of mine.  He wanted me to reverse a string
>>>>with recursion without using any additional variables or loops.  I got mine
>>>>to work by using exclusive or, but I needed an additional variable.  Can
>>>>someone help with this problem without using the additional variable?
>>>>
>>>>Thanks
>>>You can swap two variables, x and y, with the following series of exclusive
>>>or's:
>>>        x ^= y;
>>>        y ^= x;
>>>        x ^= y;
>>
>> From what he wrote I believe Leland was already doing that. The problem is
>> to write the entire function without using an additional variable. It
>> can be done! :-)
>>
>> --
>> -----------------------------------------
>> Lawrence Kirby | [e-mail]
>> Wilts, England | [e-mail]
>> -----------------------------------------